MacBook Pro thermal paste failing after a day?

Thank you for the reply,

I have actually run Apple Hardware Test and reset the SMC, (it doesn't run Apple Diagnostics since it is early 2011, only > 2012 MacBooks can run it), and AHT found no issues and of course the SMC didn’t affect it. I’ve thought about it and it seems to have boiled down to the physical cooling system not functioning. The reason I think that this would be the cause is since I didn’t change really anything between the two tests. Also I noticed on the first, it took a fairly long time for it to reach 92° C with the fans just barely above idle, but with the second the fans were roaring but the temps didn’t seem to care if the MacBook even had a cooling system at all! As you said, I’m pretty sure something in the heatsink / thermal paste part of the cooling system was the problem, as it acted like it just physically couldn’t cool the CPU.

Second, I just like using Intel Power Gadget because I’ve just used it a lot so I’m familiar with finding it and installing it quickly, and also I haven’t had too many problems with it, maybe because I work with older Macs which don’t run most of the new versions of MacOS that have some more of the enhanced security measures that can hinder using things like that. The only reason I thought it might be throttling is that it dropped the clock speed from spiking back and forth to 2.9Ghz down to a steady 2.6ghz, but that’s nowhere near below the base clock so I doubt anymore that it was throttling.

Third, the stress test I used is just terminal command “yes” (which I find absolutely hilarious) which just outputs the letter “y” as many times as possibly to the terminal window, so by using it 8 times for 8 threads, it maxes out the CPU to 99% usage (out of 100%, not like in activity monitor), making a good consistent temperature test that I like to use.

So, after the third time of replacing the thermal paste (I mentioned it at the end of my first question) the temperature went back to normal, maxing at 92° C like before, so that’s great, but I still came here because I wasn’t sure if I was doing something wrong or why that would be happening since I didn’t want to have to replace the thermal paste every other day. The good news is, this morning after letting it rest overnight I ran the “yes” test again and it had the same results (and a bit better..?) maxing at 89° C to 93° C (it goes up a bit overtime, probably because MacOS doesn’t want to run the fans at full speed until it hits ~ 95° C, so it goes up and down, also I didn’t test it for long because I still have the fear that I’m slowly toasting the CPU). So that’s great news, even if I don’t figure out why it dropped performance on the second test, at least it’s working after another reapplication of paste, so maybe I won’t have to worry about it again.

Thanks, Pyrotex7

Well what I meant was, the fans started running high in iMovie while doing image stabilization (which I believe was using the CPU, but I may be mistaken, I forget if I checked with activity monitor or not, although I know that can’t tell if it’s using both or not), so I was a little confused at only iMovie stressing the fans that much, but I agree you are right, the CPU and GPU together would stress the cooling more. I don’t remember whether or not I checked the temp in iMovie, but after I was finished with iMovie I ran the fully CPU stress test which resulted in the high CPU temps of 99°, without using the GPU. Anyway, I think I’m fine now, thank you for the advice. I think something had a rare incident of shifting the heatsink a lot which majorly depleted the cooling performance, and then after reseating it again it went back to normal.

Well, thank you both for the help. I’m probably going to close this now. When I first posted on this after I had gotten it to work once with new thermal paste I did so because I expected it to misbehave again and I didn’t want to have to wait until it did. Thankfully now it seems to be working, although now the pattern is even more confusing, but I won’t mess with it anymore.

Thanks, Pyrotex7

*On the 5th paragraph, when I said after the third time of replacing the paste, I just mean after the second stress test which had the odd results - I replaced the thermal paste twice before the first stress test, as the first time I was a bit hasty so I went back to check it and replace it again. The next day after the first stress test I ran it again and had the 99° C temps, so after that I replaced it again, which was the third time, and had fine results again after that from a couple tests.

• Well, it’s not that I can’t run it, it’s just that it doesn’t. Any Mac before 2012 will just install AHT when using Internet Recovery (opt + d) which was apple’s old blue screen retro looking version of Apple Diagnostics. Usually people use the old name and new name to differentiate, but Apple considers them the same, just the new one has an updated name and UI.

• I didn’t see anything damaged, so hopefully nothing’s physically broken. Also I don’t think it would be since I had different results each time, only related to each time I replaced the thermal paste.

• Ok, thank you for the suggestion. I’ll probably just leave this one for now, since it seems to be working now after a few tests.

Since the Macbook is working now, I’m just going sum it up to a mystery or maybe a bad thermal paste application. I’ll probably close this issue soon, I’ll just leave it for a day and see if anyone else has any thoughts on how that could’ve happened. At this point it’s not a major issue I’m just curious. Thank you a lot for the advice and suggestions.

Thanks, Pyrotex7

Sorry, to simplify my question - I know I always over detail my questions - I was confused because I replaced the thermal paste in the MacBook, and ran some tests on the CPU and got a max of 92° C. Then a day after, from being prompted by noticing high fan speed in iMovie, I ran them again on the CPU and got 99° C, which seemed odd after it stabilizing at 92° one day, and then shooting to 99° then next like most MacBooks do with old thermal paste. It’s seemed to resolve itself now after doing the repaste procedure again, but I was still curious. Also I didn’t mean I thought the thermal paste was just bad, but more in that area of for some reason it’s not doing it’s job.

Wow, that was fast.

Ok, that does make sense. If it acts up again I’ll try safe mode. By the way I have been using a fresh install. Hopefully it won’t act up again, if it does I’ll definitely try some of the stuff you’ve suggested. I probably should’ve done more testing while it was acting up, but at least it’s not a serious problem anymore.